A hearing began in a London court Thursday into whether a British day trader accused of causing a “flash crash” in American markets can be extradited to the U.S. to face charges.

Navinder Sarao, a 36-year-old who traded from his parents’ home in London, is accused of manipulating the markets in 2010 that caused a 1,000-point fall on the Dow Jones Industrial Average.

U.S. prosecutors say Sarao netted $875,000 from the move, and he faces 22 charges in America, including “spoofing”, which is the practice of buying or selling with the intent to cancel the transaction before it’s completed, the BBC reports.

The software tricks markets by generating large sell orders that push down prices. Authorities allege that Sarao made around $40 million over five years with the scheme, according to the BBC.

Sarao has denied all the charges and told a London court in May that he was just “being good at my job.”

He was arrested in April after being charged by the Justice Department was released on bail last year after spending four months in custody.